The Science Journal of the American Association for Respiratory Care
BACKGROUND: Previous studies at our institution suggested that nitric oxide (NO) can be delivered to an oxyhood with acceptable levels of nitrogen dioxide (NO2) using a large Nova Tent House (Nova Health Systems, Blackwood, NJ) at a constant FiO2. The purpose of this study was to determine if (a) hood geometry effects NO2 levels (b) increasing FiO2 results in unacceptable levels of NO2 production and (c) oxyhood delivery of NO with poses an environmental threat.
Methods: Three different oxyhoods were set to receive FiO2 = 0.40 at a total flow of 15L/m. NO was then introduced at 40 ppm. Hood brands were: ICN Pharmaceutical Ribavirin hood (ICN Pharmaceuticals, Costa Mesa, CA), ?Oxydome? (Nascor, Australia) and the 7
Results: Measured NO levels ranged from 36 to 38 ppm with a resultant FiO2 ranging from 0.36 to 0.28. NO2 was 0.7 ppm for the ICN hood and 0.5 ppm for the other two. NO/NO2 data outside the hoods are shown below. The correlation between FiO2 and NO2 was 0.983 (p < 0.0001); FiO2 = -0.245 + (0.444 * NO2), R2 = 0.967, (assumptions of normality and constant variance validated).
|Environmental Exposure Data|
|10 cm||30 cm||60 cm||PEL@30cm|
|ICN||33 / 0.6||0.8 / 0.0||0.3 / 0.0||2.5 / 0.0|
|Oxydome||30 / 0.4||1.3 / 0.0||0.5 / 0.0||3.8 / 0.0|
|Nova small||25 / 0.2||0.6 / 0.0||0.3 / 0.0||1.7 / 0.0|
|Nova large||37 / 0.9||1.5 / 0.0||0.6 / 0.0||3.5 / 0.0|
The ICN scavenging system did not decrease environmental exposure to NO/NO2.
Conclusions: All oxyhoods satisfactorily deliver NO/O2 mixtures. Scavenging is not necessary. At any significant distance from the hood NO and NO2 values are well below OSHA guidelines (NO TWA = 25ppm, NO2 = 3ppm, NO PEL = 25 ppm and NO2 STEL = 5ppm). Higher FIO2 places the patient at increased risk of NO2 exposure. Respiratory Care departments delivering NO/O2 mixtures via oxyhood should establish preset mixture limits to avoid placing their patients at increased risk.